An advanced model for self-heating effects in silicon devices is derived from first principles of irreversible thermodynamics. The resulting system of governing equations selfconsistently takes account of heavy doping effects. It is valid in both the steady state and the transient regimes. Four characteristic effects contributing to the heat generation can be identified: Joule heating, Thomson heating, recombination heating and carrier source heating.

The importance of the entropy balance equation is emphasized in order to derive the heat flux and the current relations for electrons and holes. It is shown that the heat generation implies the well known Thomson relations and is therefore consistent with the classical formulation of thermoelectricity in metals. The H-theorem is utilized in order to develope an expression of the local entropy production allowing to relate makroscopic energies to microscopic energies. Neglecting the contribution of the drift energy to the mean kinetic energy of carriers the hydrodynamic energy balance equation, supplemented by a continuity equation of potential energy, delivers the heat flow equation, which also results from principles of irreversible thermodynamics.

Numerical methods to solve the governing equations for the coupled transport
of charge carriers and heat are described.
The electrothermal nature of device behaviour during latch-up in an
IGT has been simulated.
It has been found, that simulations based on a heuristic model of
electrothermal transport tend to predict a larger save operating area
of the IGT than simulations based on the suggested rigorous
model of electrothermal interaction.
The problem of electrothermal stability due to different cooling
conditions has been investigated by computing the thermal transients
in a nonplanar GTO-thyristor.
It is shown that thermal runaway is significantly accelerated by
carrier source heat, Thomson heat and
additional contributions in the generalized Joule heat and recombination heat,
compared to simulations based on a heuristic theory of thermoelectricity.

Sat Jun 10 15:00:12 MET DST 1995